ospfd: Unify router and network LSA refresh logic with general refresher

ospfd: Unify router and network LSA refresh logic with general refresher

* (general) Get rid of the router and network LSA specific refresh timers
  and make the general refresher do this instead. Get rid of the twiddling
  of timers for router/network LSA that was spread across the code.

  This lays the foundations for future, general LSA refresh improvements,
  such as making sequence rollover work, and having generic LSA delays.

* ospfd.h: (struct ospf) Bye bye to the router-lsa update timer thread
  pointer.
  (struct ospf_area) and to the router-lsa refresh timer.
* ospf_interface.h: Remove the network_lsa_self timer thread pointer
* ospf_lsa.h: (struct ospf_lsa) oi field should always be there, for benefit
  of type-2/network LSA processing.
  (ospf_{router,network}_lsa_{update_timer,timer_add}) no timers for these
  more
  (ospf_{router,network}_lsa_update) more generic functions to indicate that some
  router/network LSAs need updating
  (ospf_router_lsa_update_area) update router lsa in a particular area alone.
  (ospf_{summary,summary_asbr,network}_lsa_refresh) replaced by the general
  ospf_lsa_refresh function.
  (ospf_lsa_refresh) general LSA refresh function